U.S. patent number 6,913,570 [Application Number 10/713,638] was granted by the patent office on 2005-07-05 for method and apparatus for producing a composite structural panel with a folded material core.
This patent grant is currently assigned to Airbus Deutschland GmbH. Invention is credited to Rainer Kehrle.
United States Patent |
6,913,570 |
Kehrle |
July 5, 2005 |
**Please see images for:
( Certificate of Correction ) ** |
Method and apparatus for producing a composite structural panel
with a folded material core
Abstract
A folded core structure is produced by embossing fold lines into
a flat planar material web, initiating folds along the fold lines
on the upper and lower surfaces of the material web, proceeding
with the formation of the folds along the fold lines to deform the
material web from its two-dimensional starting configuration to a
three-dimensional folded configuration, and post-processing the
folded material web to stabilize or fix the folded configuration
thereof. A composite structural panel is produced by bonding a
cover layer onto at least one surface of the folded core structure.
An apparatus preferably includes embossing or creasing rolls to
form the fold lines in the material web, air nozzles or folding
rolls to initiate the folding process, bristle brush rolls to
complete the folding process, and further folding rolls to enhance
and fix the folded configuration, optionally in connection with
heating, cooling, applying a coating onto, or impregnating a resin
or binder into the material web.
Inventors: |
Kehrle; Rainer (Stuttgart,
DE) |
Assignee: |
Airbus Deutschland GmbH
(Hamburg, DE)
|
Family
ID: |
32240027 |
Appl.
No.: |
10/713,638 |
Filed: |
November 13, 2003 |
Foreign Application Priority Data
|
|
|
|
|
Nov 14, 2002 [DE] |
|
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102 52 941 |
|
Current U.S.
Class: |
493/451;
493/463 |
Current CPC
Class: |
E04C
2/326 (20130101); B31D 3/005 (20130101) |
Current International
Class: |
B31D
3/00 (20060101); E04C 2/32 (20060101); B31F
001/00 () |
Field of
Search: |
;493/451,463,955,966 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Kim; Eugene
Attorney, Agent or Firm: Fasse; W. F. Fasse; W. G.
Claims
What is claimed is:
1. A method of producing an article comprising a folded core
structure, maid method comprising the steps: a) providing a
material web having an initial flat planar configuration; b)
subjecting said material web having said initial flat planar
configuration to a continuous pretreatment process comprising
forming a repeating pattern of fold lines in said material web from
at least one of an upper surface and a lower surface thereof such
that said material web with said repeating pattern of fold lines
still has said flat planar configuration; c) after said step b),
initiating a formation of folds in said material web along said
fold lines on at least one of said upper surface and said lover
surface; d) after said step c), carrying out and completing said
formation of said folds along said fold lines to deform said
material web from said initial flat planar configuration into a
three-dimensionally folded configuration having an increased
thickness relative to said flat planar configuration, whereby said
initial flat planar configuration of said material web undergoes a
longitudinal contraction in a longitudinal direction of said
material web, a transverse contraction in a transverse direction of
said material web, and a thickness expansion in a direction of said
thickness; and e) after said step d), post-treating said material
web to stabilize maid folded configuration thereof, to produce
therefrom a folded core structure.
2. The method according to claim 1, further comprising, after said
step e), a further step of arranging and attaching a respective
cover layer on at least one major surface of said folded core
structure to produce therefrom a composite structural panel.
3. The method according to clam 1, wherein said step a) comprises
providing a web comprising composite reinforcement fibers as said
material web.
4. The method according to claim 1, wherein said longitudinal
contraction, said transverse contraction and said thickness
expansion all occur simultaneously in a single-stage folding
process in said step d), and wherein said single-stage folding
process is carried out without mechanical guidance of said material
web parallel to said fold lines.
5. The method according to claim 1, wherein said transverse
contraction and said thickness expansion occur together in a first
stage of a folding process in said step d) without said
longitudinal contraction, and thereafter said longitudinal
contraction occurs in a second stage of said folding process, and
further comprising compensating for a travel distance variation of
edge portions of said material web relative to a center portion of
said material web during said first stage of said folding
process.
6. The method according to claim 1, wherein said pretreatment
process comprises at least one of embossing, impressing, creasing,
scoring, and perforating said fold lines into said material
web.
7. The method according to claim 1, wherein said pretreatment
process further comprises at least one of heating said material
web, cooling said material web, etching said material web, applying
a binder to said material web, and impregnating a resin into said
material web.
8. The method according to claim 1, wherein said post-treating in
said step e) comprises at least one of embossing, pressing,
creasing, scoring, and perforating said material web.
9. The method according to claim 1, wherein said post-treating in
said step e) comprises at least one of heating said material web,
cooling said material web, etching said material web, applying a
binder to said material web, and impregnating a resin into said
material web.
10. The method according to claim 1, wherein said initiating of
said formation of maid folds in said step c) comprises directing a
flow of a fluid at at least one of said upper surface and said
lower surface of said material web.
11. The method according to claim 1, wherein said initiating of
said formation of said folds in said step c) comprises mechanically
contacting at least one of said upper surface and said lower
surface of said material web so as to begin said formation of said
folds.
12. The method according to claim 1, wherein said completing of
said formation of said folds in said step d) comprises passing said
material web between two bristle brush rolls that respectively
contact said upper surface and said lover surface of said material
web, whereby respective bristles of said two bristle brush rolls
intermesh with each other as said material web is deformed and
folded along said fold lines between said respective bristles of
said two bristle brush rolls.
13. The method according to claim 1, wherein said step b) comprises
forming said repeating pattern of fold lines in said material web
from both said upper surface and said lower surface.
14. The method according to claim 1, wherein said repeating pattern
of fold line comprises respective pluralities of said fold lines
intersecting one another in respective star patterns at respective
intersections.
15. The method according to claim 1, wherein said repeating pattern
of fold lines forms a continuous field of surface areas that are
respectively bordered and enclosed by said fold lines and that
border one another along said fold lines in said material web.
16. A method of producing a folded structure, comprising the steps:
a) providing a material web having an initial flat planar
configuration; b) forming a repeating pattern of fold lines in said
material web by at least one of embossing, impressing, creasing,
scoring, and perforating said fold lines into said material web
still having said flat planar configuration; c) initiating a
formation of folds in said material web along at least some of said
fold lines by directing jets of a fluid at said material web; d)
passing said material web between two intermeshing bristle brush
rolls so as to further form said folds in said material web,
whereby said initial flat planar configuration of said material web
undergoes a longitudinal contraction in a longitudinal direction of
said material web, a transverse contraction in a transverse
direction of said material web, and a thickness expansion in a
direction perpendicular to said longitudinal direction and said
transverse direction, from said initiating of said formation of
said folds through said further forming of said folds, so as to
deform said material web from said initial flat planar
configuration to a resulting three-dimensionally folded
configuration; and e) stabilizing said three-dimensionally folded
configuration by at least one of accentuating, pressing,
strengthening, rigidifying, and fixing said folds, so as to form a
folded structure of said material web having said
three-dimensionally folded configuration.
17. An apparatus for producing a structure comprising a folded core
structure fabricated from a planar material web, said apparatus
comprising: a first arrangement for pre-treating the material web
from at least one of an upper surface and a lower surface thereof
to form fold lines therein while maintaining an initial flat planar
configuration of the material web; a second arrangement for
initiating a folding process of forming folds along at least some
of the fold lines in the material web; a third arrangement for
proceeding with the folding process and longitudinally retarding
the material web, including at least one pair of counter-rotating
bristle brush rolls or bristle brush conveyor belts to form a
folded structure; and a fourth arrangement for post-treating the
material web on the upper surface and the lower surface thereof to
stabilize the folded structure.
18. The apparatus according to claim 17, wherein said first
arrangement comprises a pair of counter-rotating rolls including at
least one roll having a structured surface, a pair of link chains
or belts including at least one link chain or belt having a
structured surface, or a conveyor belt having a structured
surface.
19. The apparatus according to claim 18, further comprising an
apparatus for varying a running length between said first
arrangement for pre-treating the material web and said second
arrangement for initiating the folding process.
20. The apparatus according to claim 17, wherein said third
arrangement further comprises an arrangement for contracting a
transverse width and expanding a thickness of the material web,
including a pair of counter-rotating rolls having a structured
surface and an adjustable axis spacing, or a comb-like arrangement
with an adjustable gap, as well as an arrangement for compensating
a running length of the material web.
21. The apparatus according to claim 20, further comprising a
mechanical arrangement or a pneumatic arrangement operating with a
fluid pressure for deforming the material web in a direction of the
transverse width.
22. The apparatus according to claim 17, wherein said second
arrangement comprises a row of movably arranged fluid nozzles.
23. The apparatus according to claim 17, wherein said third
arrangement comprises a row of movably arranged fluid nozzles.
24. The apparatus according to claim 17, wherein said fourth
arrangement comprises a pair of counter-rotating rolls, conveyor
belts, or link chains or belts, having a structured surface
including a pattern of edges, and wherein the folded structure has
a pattern corresponding to a circumferential development of the
pattern of edges of the structured surface of the fourth
arrangement.
25. The apparatus according to claim 24, further comprising an
arrangement for heating, cooling, coating or impregnating the
material web.
26. The apparatus according to claim 17, further a comprising an
arrangement for applying at least one additional material web onto
the folded structure.
27. The apparatus according to claim 17, further comprising an
arrangement for cutting and transporting-away the material web.
28. The apparatus according to claim 17, wherein said first
arrangement is adapted to pre-treat the material web from both the
upper surface and the lower surface.
Description
PRIORITY CLAIM
This application is based on and claims the priority under 35
U.S.C. .sctn.119 of German Patent Application 102 52 941.8, filed
on Nov. 14, 2002, the entire disclosure of which is incorporated
herein by reference.
FIELD OF THE INVENTION
The invention relates to a method as well as an apparatus for
producing a lightweight core structure from a web of a thin
foldable starting material, and then covering the core structure
with one or two cover layers to form a composite structural panel
thereof.
BACKGROUND INFORMATION
It is generally known to form lightweight structural panels
including a lightweight core structure sandwiched between two cover
layers. The core structure typically is lightweight yet strong,
because it has a configuration including hollow spaces as well as
interconnected material webs or the like. Typical examples of such
core structures include corrugated sheets, honeycomb cellular
structures, and the like. Known core structures have a great
variety of different configurations, and are made of a great
variety of different materials.
The resulting composite structural panels, which respectively
include such a core structure sandwiched and bonded between two
cover layers, are used in many different applications, for example
as lightweight structural panels or shell elements for walls,
floors, and ceilings in transport aircraft, motor vehicles, ships,
and trains. Such panels are similarly used in the interior and
exterior construction of buildings. A further application of such
composite structural panels is as filler panels or core panels of
veneered furniture, for example, in the furniture manufacturing
industry. Yet another application, especially in the case of
corrugated cardboard panels, is the manufacture of crates, cartons,
boxes and other packing materials from such composite structural
panels.
Separately, it is known to form folded structures for various
applications through the use of various different methods. These
folding methods for folding sheet or web materials can be divided
into intermittent or discontinuous processes, for example as
described in U.S. Pat. No. 5,234,727, as well as continuous
processes. Such continuous processes, in turn, can be divided into
processes with a coupled or mutual lengthwise and crosswise
contraction with a simultaneous expansion in the thickness
direction of the starting material web (with a single-stage folding
operation, for example as disclosed in U.S. Pat. No. 5,947,885),
and processes in which the material web is first subjected to a
crosswise contraction and is subsequently subjected to a
deformation in the lengthwise direction of the material (in a
two-stage folding operation, for example as disclosed in U.S. Pat.
No. 4,012,932).
The continuous folding of long or essentially endless material webs
necessarily involves an inexact deformation of the material in a
mathematical and geometrical sense. Therefore, it is difficult,
complicated, and costly to realize an actual mechanical apparatus
that is to carry out the continuous folding of such a long material
web in an exact manner, because a distortion or deformation of the
material web arises, which may be within the deformation range of
the elastic properties of the, material web and is difficult to
control. In all of the above mentioned publications, the folding is
carried out by a folding mechanism that accompanies the folding
operation along the fold edges or the fold edges and surfaces.
SUMMARY OF THE INVENTION
In view of the above, it is an object of the invention to provide a
method and an apparatus for producing a core structure of a
composite structural panel, in which the starting material web is
not stretched or compressed, and is also not provided with punched
or cut-out openings, slits or cuts, yet is continuously folded with
precise fold angles, precise fold lines, and precise resulting
folded surfaces that are true to the intended and desired folded
configuration. The invention further aims to avoid or overcome the
disadvantages of the prior art, and to achieve additional
advantages, as apparent from the present specification.
The above objects have been achieved according to the invention in
a method of manufacturing a composite structural panel including a
folded core structure bonded or otherwise attached to one or two
cover layers. The starting material for manufacturing the core
structure is a thin foldable material provided as a web, preferably
of indefinite length, and may comprise a fiber material web, a
fibrous semi-fabricated product, a pre-preg web (namely a fibrous
semi-fabricated product web that is pre-impregnated with a curable
resin or the like), a paper web, a cardboard web, a film web, a
foil web, a metal sheet or the like. The flat web or sheet of the
starting material is folded into a multi-surfaced, spatially
three-dimensional, developable structure through the folding
process, in which the starting material is subjected to a
contraction in the width direction and the lengthwise direction as
well as an expansion in the third spatial or thickness direction,
relative to the dimensions of the starting material web.
More particularly, according to the inventive method, the material
web provided in an initial flat planar un-folded condition is first
subjected to a pre-processing step in which fold lines that allow a
subsequent buckling or collapsing and precise folding of the
material along these fold lines are formed in the material web.
Particularly, this pre-processing or pre-treatment step is a
continuous process in which plural curved or straight fold lines
that meet or intersect each other in star-like repeating patterns,
with respective surface areas bounded between the fold lines, are
embossed, impressed, scored or creased into the material web from
the upper surface and the lower surface thereof. Next, after the
fold lines have been formed, the folding process is initiated along
the fold lines from the upper surface and the lower surface of the
material web. Then, the initiated folding process is progressively
continued and completed to produce folds in the material web along
the fold lines, whereby the material web is deformed and
reconfigured from its two-dimensional initial configuration to a
three-dimensional folded structure or configuration. After the
folding process, the material web is further post-processed or
post-treated in order to stabilize the achieved folded structure,
e.g. by accentuating and/or fixing the folds.
According to further special aspects of the invention, the
following additional features can be achieved. The fold lines or
the resulting folded edges can exhibit a curved shape. The thin
planar starting material can be further pre-treated by embossing,
impressing, perforating, scoring, creasing, coating with a coating
material, impregnating with a resin or other impregnating material,
heating or cooling, along the fold lines or within the surface
areas bounded by the fold lines while avoiding the fold lines.
Also, the resulting folded core structure can be produced with a
three-dimensional spatial configuration of which the folding
pattern repeats itself.
According to the inventive method, it is possible to use flexible,
limp or flaccid starting materials, such as woven webs for example,
which inherently by themselves would not exhibit or develop any
folding mechanism. Such materials can be made suitable for the
present inventive folding process, for example by coating them with
binders or by impregnating them with a synthetic resin, and further
by pre-processing the fold lines, for example by partially scoring
or perforating or creasing the woven web material along the
intended fold lines, so that folded edges allowing a precise
collapsing or buckling of the material along the fold lines will be
formed.
Furthermore, with the inventive step of initiating the folding;
process along the fold lines formed in the pre-treatment step, the
pre-treated material itself serves to provide or develop the
folding mechanism, due to the pre-treatment and pre-forming of the
fold lines, without requiring any folding template such as a master
fold sheet or the like and without requiring a folding guide. In
fact, the initiation of the folding process can be carried out
without even contacting the pre-treated web, for example by means
of air jets directed at appropriate locations on the upper surface
and the lower surface of the pre-treated material web.
Still further according to the invention, the folding process that
is carried out after the initiation of the folds along the
pre-formed fold lines serves to deform and reconfigure the thin
two-dimensional starting material into a three-dimensional folded
configuration with folded edges that are folded precisely at
prescribed angles or extend along prescribed curves so as to result
in the final three-dimensional folded configuration having accurate
desired fold angles and accurate desired surfaces bounded between
the folded edges. Thereby, in the folding process, the core
structure undergoes both a length variation as well as a width
variation relative to the two-dimensional initial configuration of
the material web. This folding process is carried out as a
continuous through-flow process in which the starting material is
continuously fed into the folding apparatus carrying out the
folding process, and the resulting folded core structure can be
continuously removed therefrom.
The core structures produced according to the inventive method are
characterized advantageously by a low density and simultaneously by
a high bending stiffness and compressive stiffness as well as a
high strength, especially in combination with the cover layers
arranged and bonded thereon to form the complete structural panel.
Due to the particular selected starting material, a good noise
insulation characteristic can also be achieved, which can be
further improved by perforation of the cover layers. A further
advantage of the invention is a significant cost reduction achieved
by the substantial increase in the production speed, which is
achieved in the continuous fabrication using the method and
apparatus of the invention.
The possibility of folding the starting materials also along curved
folded edges rather than or in addition to straight folded edges
greatly improves the compressive stiffness and strength and
therewith substantially expands the field of application of these
core structures, because structures that are folded along curved
folded edges are bendable or curvable overall, as opposed to
structures that are only folded along straight folded edges. When
such a curved or non-planar folded core structure is bonded to
curved non-planar cover layers, the curved folded edges of the core
structure will lie in contact with the respective upper and lower
cover layer along the entire length of the folded edge, and thus
may be advantageously glued or otherwise bonded to the respective
cover layer along this entire folded edge. This achieves an
especially good bonding connection between the core and the cover
layers.
The above objects have further been achieved according to the
invention in an apparatus for forming a composite structural panel,
and particularly for carrying out the inventive method. The
inventive apparatus includes a device or arrangement for
pre-treating or pre-processing the starting material web on the
upper surface and the lower surface thereof in order to form
therein fold lines that will allow a collapsing or buckling of the
material web along these fold lines. The apparatus further includes
a device or arrangement for initiating the folding process along
the previously formed fold lines. The apparatus also includes a
device or arrangement for carrying out the additional deformation,
reconfiguration, and/or retardation of the material web to further
carry out the folding process along the previously initiated folds
on the fold lines, with at least one pair of counter-rotating
bristle brush rolls or bristle brush conveyor belts. The apparatus
still further includes a device or arrangement for post-processing
or post-treating the material web from the upper surface and the
lower surface thereof in order to stabilize the folded structure by
enhancing and/or fixing the folds for example.
According to a further development of the apparatus according to
the invention, at least one counter-rotating pair of rolls, a pair
of conveyor belts, or a pair of link chains or belts is provided
for carrying out the pre-processing or pre-treatment of the planar
starting material web. In this context, at least one of the two
rolls, conveyor belts, or link chains or belts has a structured
surface, which cooperates with a smooth non-structured surface of
the opposite or complementary element to form the fold-lines in the
planar starting material web. Throughout this disclosure, the term
"structured surface" refers to a surface that is not smooth, but
rather includes profiled protrusions such as ridges or the like, at
locations in a pattern corresponding to the pattern of fold lines
to be formed in the material web. Thus, the respective roll,
conveyor belt, or link chain can be provided with protruding
ridges, creasing blades, scoring blades, perforating blades or the
like, which cooperate with the smooth surface of the counter-roll
or other counter element. The smooth surface of the counter element
may have an elastic resilient surface covering, to allow the
protruding ridges or the like of the structured surface of the
other element to press into this resilient surface covering in
order to form the fold lines on the material web. Alternatively,
the counter-element may have a surface provided with recesses
corresponding to and cooperating with the protruding ridges or the
like of the opposite roll or other element. In addition to or
instead of the just-described elements with a structured surface,
the pre-treating arrangement can additionally or alternatively
include a device for heating or cooling certain zones of the
material web, and/or a device for coating or impregnating the
material web.
According to the invention, the device or arrangement for
initiating the folding process along the previously formed fold
lines can comprise at least one row of fluid nozzles, preferably
compressed air nozzles, which are arranged to be movable relative
to the material web. Respective groups or arrays of such nozzles
are arranged above and below the material web and are oriented
opposite one another so as to direct jets of fluid, e.g. compressed
air, onto the upper surface and the lower surface of the material
web, e.g along the fold lines and/or at appropriate surface areas
for initiating folds along the fold lines. Thereby, the air jets
from below the material web push up and initiate the formation of
fold peaks in the material web, while the air jets above the
material web push down along corresponding fold lines to initiate
the formation of fold valleys in the material web.
A further embodiment of the device or arrangement for initiating
the folding process according to the invention comprises a
mechanical arrangement that physically contacts and touches the
material web either in a point-wise manner or along individual fold
lines, both from the upper surface and the lower surface of the
material web, so as to begin the folding process. In such a
mechanical device, mechanical fingers or protrusions or disk
elements take the place of the air jets discussed above in the
fluid nozzle arrangement for initiating the folding process.
The device or arrangement for initiating the folding process
according to the invention can alternatively or additionally
comprise a contraction and expansion device that simultaneously
carries out a crosswise or transverse contraction and a vertical or
thickness-directed expansion of the material web along the fold
lines, but does not yet cause a longitudinal contraction of the
material web. This device comprises at least one pair of
counter-rotating rolls, or at least one arrangement with a
comb-like gap in which the material web is caused to contract in
the crosswise or transverse direction perpendicular to its
longitudinal extension, and to expand in the vertical thickness
direction. During that process, a compensation of the running
length respectively of the center of the material web and of the
edges of the material web is carried out by a suitable targeted
deflection of the material web in its middle or center area
relative to its edges. After the crosswise or transverse
contraction of the material web (in connection with forming the
folds along longitudinally extending fold lines), an alternating
perpendicular displacement of the web is carried out by means of an
apparatus operating with compressed air or by means of a suitable
mechanical arrangement, so as to form the peaks and valleys along
the transversely extending fold lines, which thereby causes a
longitudinal contraction of the material web.
A further varied embodiment of an apparatus for deformation,
reconfiguration, and/or retardation (e.g. longitudinal contraction)
of the material web according to the invention comprises compressed
air nozzles that blow against the upper surface and the lower
surface of the folded material web in a direction contrary to the
forward production travel direction. This achieves or supports a
contraction of the material web with respect to the longitudinal
production travel direction, which is involved in the folding
operation of forming the peaks and valleys especially along
transversely extending fold lines.
An example embodiment of the device or arrangement for
post-treating or post-processing the folded material web comprises
at least one pair of counter-rotating rolls, conveyor belts, or
link chain or belt mechanisms, having a structured surface of which
the developed (e.g. circumferential) projection corresponds to the
folded structure of the folded material web. Alternatively, the
structured surface of the post-processing elements contacts the
folded material web at least along the folded edges thereof, so as
to reinforce and stabilize the folded configuration of the material
web. Furthermore, the post-treatment arrangement may include an
apparatus for coating, impregnating, heating, or cooling the
material web, so as to further stabilize or permanently fix the
folded configuration of the folded material web.
Furthermore, the inventive apparatus preferably includes a
post-treating or post-processing device for applying at least one
material web as a layer, e.g. the cover layer, onto at least one
surface of the folded core structure. The material used for the
cover layer(s) in this regard may be any conventionally known cover
layer material of a lightweight structural panel. Moreover, the
post-treating apparatus can include a cutting device and a
transport device for carrying away finished cut segments of the
folded core structure or the finished composite structural
panel.
BRIEF DESCRIPTION OF THE DRAWINGS
In order that the invention may be clearly understood, it will now
be described in connection with example embodiments thereof, with
reference to the accompanying drawings, wherein:
FIG. 1 is a schematic side view of a first embodiment of an
apparatus for manufacturing a composite structural panel including
a folded core structure according to the invention;
FIG. 2 is a schematic top plan view of the apparatus according to
FIG. 1;
FIG. 3 is a schematic side view generally corresponding to FIG. 1,
but showing a second embodiment of an apparatus according to the
invention;
FIG. 4 is a schematic top plan view of the apparatus according to
FIG. 3;
FIG. 5 is a schematic side view of a single folding roll;
FIG. 6 is a schematic perspective view of a pair of folding
rolls;
FIG. 7 is a schematic view of a further embodiment of a pair of
folding rolls;
FIG. 8 is a schematic perspective view of a comb-like arrangement
for carrying out or guiding a crosswise contraction and thickness
expansion of the material web;
FIG. 9 is a schematic perspective view of an alternative
arrangement using a roll pair for carrying out the crosswise
contraction and thickness expansion of the material web;
FIG. 10 is a schematic diagram of a fold structure for reference
and for explanation of different embodiments of fold structures
that are respectively illustrated in FIGS. 11 to 21; and
FIGS. 11 to 21 are schematic diagrams of respective different fold
structures having different fold patterns.
DETAILED DESCRIPTION OF A PREFERRED EXAMPLE EMBODIMENT AND OF THE
BEST MODE OF THE INVENTION
FIGS. 1 and 2 schematically show a first embodiment of an apparatus
according to the invention for carrying out the method according to
the invention. Namely, the apparatus shown in FIGS. 1 and 2 is for
producing a composite structural panel SP including a core
structure sandwiched and bonded between two cover layers C. The
core structure is produced by folding a material web M, for example
of paper or cardboard or resin-impregnated fiber. In the present
embodiment, the folding process is a single stage folding process
involving a transverse contraction, a longitudinal contraction, and
a thickness expansion of the material web M occurring
simultaneously. In this folding process, first, fold lines are
formed in the initially flat planar configuration M1 of the
material web M, and then fold valleys V, shown by solid lines, and
fold peaks P, shown by dashed lines, are formed in the material web
along the respective associated fold lines.
More particularly, the apparatus includes a first structured roll 1
with a structured surface, e.g. a surface with protruding ridges or
creasing blades or the like, as well as a first counter roll 2
which is preferably a smooth roll with a smooth surface, such as a
smooth elastically yielding surface. The material web M with its
initial flat planar configuration M1 passes through the nip between
the first pair of rolls 1 and 2, whereby the protrusions or
creasing blades of the structured surface of the structured roll 1
press against the smooth surface of the smooth roll 2 with the
material web M therebetween. Thereby the creasing blades or the
like form valley fold lines V in the upper surface of the material
web M. In this context, the repetitive pattern of the protrusions
or creasing blades on the structured surface of the structured roll
1 forms the corresponding developed pattern of the valley fold
lines V on the material web M.
Next, the still-planar material web M proceeds to a second roll
pair including a second smooth counter roll 3 cooperating with a
second structured roll 4. These rolls 3 and 4 operate similarly as
the rolls 2 and 1, respectively. Namely, as the material web M
passes through the nip between the two rolls 3 and 4, the
protrusions or creasing blades of the structured roll 4 emboss or
press peak fold lines P into the material web M from the bottom
surface thereof. Thus, upon exiting the second pair of rolls 3 and
4, the material web M now has a still-planar configuration M2, but
with peak fold lines P and valley fold lines V embossed, pressed,
creased or scored in the material thereof.
Next, the material web is advanced in the forward travel direction
to a pair of movable air nozzle arrangements 5 and 6, which are
respectively arranged above and below the material web M, and which
each respectively include plural compressed air jet nozzles. The
air jet nozzles are located appropriately, and can be either
continuously or intermittently supplied with compressed air, so as
to direct compressed air jets at suitable locations, e.g. along the
respective fold lines P and V, so as to push the peak fold lines P
upwardly and push the valley fold lines V downwardly relative to
the initial flat plane of the material web. In this manner, the air
jets directed from the air nozzle arrangements 5 and 6 initiate the
folding process, i.e. initiate the formation of folds in the proper
directions about the embossed fold lines P and V.
Next, the material web M with the initiated folds proceeds from the
air nozzle arrangements 5 and 6 to a pair of bristle brush rolls 9
and 10 arranged respectively above and below the material web M.
Thereby, the folds along the fold lines in the material web M that
were initiated by the air nozzle arrangements 5 and 6 are now
further developed and folded by the mechanical pressing contact
exerted by the intermeshing bristles of the brush rolls 9 and 10 in
a somewhat flexible and yielding manner. Thereby, as the folds in
both longitudinal and transverse directions (and/or diagonal
directions) in the material web are developed, the web undergoes a
contraction in both the longitudinal travel direction and in the
transverse width direction, while simultaneously undergoing an
expansion in the vertical height or thickness direction.
As can be seen in FIG. 1, the thickness of the material web
increases as the folding process progresses from the initiation at
the air nozzle arrangements 5 and 6 to the completion thereof at
the brush rolls 9 and 10. Simultaneously, as can be seen in FIG. 2,
the transverse width of the material web contracts as the folding
process progresses between the air nozzle arrangements 5 and 6 and
the brush rolls 9 and 10. Also, the brush rolls 9 and 10 retard or
decelerate the forward travel of the material web to accommodate or
even to cause the longitudinal contraction of the material web as
the folding process progresses. The material web M then exits from
the brush rolls 9 and 10 with the finished folded configuration
M3.
As the folding process progresses between the air nozzle
arrangements 5 and 6 and the brush rolls 9 and 10, the material web
M and the progress of the folding thereof can be constrained and
guided through an expansion/contraction guide arrangement 7 and 8
shown schematically in FIG. 1. This guide arrangement 7 and 8 may
comprise simple plates 7 and 8 arranged above and below the
material web M with an expanding vertical distance therebetween.
Such plates 7 and 8 simply constrain and guide the vertical
thickness expansion without guiding or causing the transverse
contraction due to folding along longitudinally extending fold
lines. Thus, with such plates 7 and 8, a single-stage compound
folding as described above progresses between the air nozzles
arrangements 5 and 6 and the brush rolls 9 and 10. Alternatively
(as will be described further below), the guides 7 and 8 may be
replaced with plates having guide channels that taper relative to
each other in the transverse width direction as the height or
vertical gap spacing increases, so as to guide and develop the
transverse folding of the longitudinally extending fold peaks and
fold valleys as they are progressively formed in the transition
from the air nozzle arrangements 5 and 6 to the brush rolls 9 and
10.
After exiting from the brush rolls 9 and 10, the material web M
with the folded configuration M3 is then transported between the
intermeshing or interengaging nip of two special after-treatment or
post-processing rolls 11 and 12 so as to stabilize and fix the
folded configuration M3 and thus form a stabilized or fixed folded
configuration M4. In this embodiment, the rolls 11 and 12 are fold
stabilizing rolls that respectively have interengaging structured
surfaces with a developed contour pattern corresponding to the fold
pattern. Thereby these rolls can further emboss and thus sharpen or
emphasize the folded edges of the folded structure. These rolls 11
and 12 may additionally be heated or cooled or further combined
with a resin coating device or resin impregnating device so as to
contribute to the resin-fixing of the folded configuration M3 of
the material web M to thereby form the fixed or stabilized
configuration M4 of the folded core structure.
At this stage, the completed, folded, fixed material web forming
the core structure M4 can be continuously withdrawn from the
folding process, and can be further cut into separate core panels
(e.g. by any known cutting device) and transported (e.g. by any
known transport device such as a conveyor) or stored as such for
later use. Alternatively, the continuous core structure exiting the
folding process, or individual cut core panels thereof, can be
directed into a further process for bonding at least one cover
layer C onto at least the upper surface or the lower surface of the
core structure. This is schematically indicated in FIG. 1, where
two cover layers C are provided from rolls 20 and 21, and are then
laminated and bonded onto the core structure by laminating rolls 22
and 23. This can be achieved by heat-lamination or with an
additional adhesive if necessary, or in any conventionally known
manner of applying and bonding a cover layer onto a core structure
to form a composite structural panel SP thereof. The laminated
structural panel SP can be continuously or piece-wise removed from
the output end of the process.
FIGS. 3 and 4 show a second embodiment of an apparatus and method
for forming a folded core structure (which can then further be used
to form a composite structural panel as described above). The
apparatus and process of FIGS. 3 and 4 have much overlap and
correspondence with those of FIGS. 1 and 2, and a redundant
description of the corresponding components and process steps will
be omitted. The same reference numbers are used to identify
corresponding features in the embodiment of FIGS. 3 and 4 as in the
embodiment of FIGS. 1 and 2.
The main difference between the first embodiment of FIGS. 1 and 2
and the second embodiment of FIGS. 3 and 4 is that the first
embodiment involves a single-stage total compound folding process,
while the second embodiment involves a two-stage folding process
with a transverse contraction and thickness expansion in a first
stage followed by a longitudinal contraction in a second stage. In
this regard, the apparatus of FIGS. 3 and 4 comprises an additional
of a pair of transverse contraction rolls 13 and 14 between the
second pair of fold line creasing rolls 3 and 4 and the pair of air
nozzle arrangements 5 and 6, and particularly at a location
proximate to and just upstream of the air nozzle arrangements 5 and
6. This pair of rolls 13 and 14 includes relatively deeply
intermeshing or interengaging circumferential V-profile discs or
roll segments which cause the material web M to be at least
partially folded in a corrugated or zig-zag folded fashion in the
transverse width direction (i.e. along longitudinally extending
folded edges), while undergoing a corresponding transverse
width-wise contraction. Namely, this pair of rolls 13 and 14
already carries out the folding and contraction of the material web
M in the transverse or width direction along longitudinally
extending fold lines, before the web even reaches the air nozzle
arrangements 5 and 6, which then initiate the folding of the web
along transversely extending fold lines. This initiated folding is
further carried out and completed by the brush rolls 9 and 10,
while the web travel is also decelerated or retarded in the travel
direction in connection with the longitudinal contraction of the
web, in a similar manner as described above in connection with
FIGS. 1 and 2.
While carrying out the transverse or width-wise contraction of the
material web M, a compensation of the forward linear travel
distance of the web must be carried out, because otherwise a
portion of the material web M along the longitudinal center line
thereof would have to travel a shorter distance than portions of
the web along the outer edges thereof, as is apparent in the top
plan view of FIG. 4. In order to compensate for this difference,
the material web preferably passes over a skimming or gliding
support in the shape of an arch or curve as seen on a plane
perpendicular to the longitudinal travel direction of the material
web. Thus, by passing over this support as schematically shown at
30 in FIG. 3, the central portion of the material web M is caused
to bulge upwardly relative to the edge portions of the material
web, or alternatively the central portion is allowed to sag
downwardly relative to the edge portions, so that the travel
distance between the roll pair 3 and 4 and the roll pair 13 and 14
is the same for all portions of the material web, despite the
transverse or width-wise contraction of the material web.
The further processing of the web downstream from the brush rolls 9
and 10 may be the same as discussed above in connection with FIGS.
1 and 2. Additionally, as may also be provided in the apparatus of
FIGS. 1 and 2, FIG. 4 schematically shows optional further
post-treating devices 15 and 16, which, for example, carry out
heating, cooling, resin-impregnation, and/or binder-coating of the
material web, upstream and/or downstream of the fold-stabilizing
rolls 11 and 12. Thereby, these devices 15 and/or 16 contribute to
the stabilizing and fixing of the folded structure M3 to form the
stabilized folded structure M4 of the folded core structure.
FIG. 5 shows a single folding roll or fold-stabilizing 11 that
comprises a structured surface 11A on its outer circumference. In
FIG. 6, a pair of two of such folding rolls 11 and 12 is shown in
the operational intermeshed or interengaged condition, whereby the
two rolls 11 and 12 are counter-rotating, with the material web
passing through the intermeshing nip therebetween. The rolls 11 and
12 each comprise an even number (in this case four) of segments
with alternating right-hand and left-hand (or clockwise and
counterclockwise) helical configurations 11B and 11C about the
circumference. Namely, the respective segments are formed
substantially as alternating segments of clockwise and
counterclockwise helical threadings that intersect each other. The
pattern of these segments 11B and 11C, in a circumferential
development thereof, corresponds to the pattern of fold lines to be
formed on the material web as described above. In order to finish
and stabilize, or to initiate the folding process of zig-zag folded
structures with particular characteristics, the respective rolls
may comprise an involute surface 11D, namely having a
circumferential contour based on an involute at each section plane
perpendicular to the roll axis. Further in this context, each roll
is divided into an even number of such segments. A coupling of the
counter-rotation of the folding rolls 11 and 12 can be carried out
mechanically by means of toothed gears, or chains on sprocket
wheels, or through electronic regulation.
FIG. 7 schematically shows an alternative embodiment of a pair of
folding rolls 11' and 12' according to a varied embodiment, with an
even number (in this case two) of segments 11A' and 12A' with
alternating right-hand and left-hand or clockwise and
counterclockwise threading slopes. In this case also, the pair of
rolls 11' and 12' can be coupled to each other mechanically by
toothed gear wheels or by chains on sprocket wheels, or by
electronic regulation.
FIG. 8 schematically represents a device for supporting and guiding
the transverse or width-wise contraction and vertical expansion of
the material web during the folding process, including two
comb-like expansion/contraction guides 7' and 8' with an adjustable
gap 17 therebetween. This arrangement represents an alternative of
the expansion/contraction guides 7 and 8 discussed above and shown
schematically in FIG. 1. This embodiment of the guides 7' and 8' is
especially for a two-stage folding process, for example as takes
place in FIGS. 3 and 4 using the expansion/contraction rolls 13 and
14 to carry out a transverse or width-wise contraction and folding
separately from and before the longitudinal contraction and
folding. As the material web is folded along longitudinally
extending fold lines in at least one folding stage, the material
web passes through the adjustable gap 17 between the opposite end
faces 7A' and 8A' of the opposite plate-shaped guide members 7' and
8'. These opposed end faces 7A' and 8A' are respectively provided
with corresponding wavy or corrugated structures, which receive and
guide the longitudinally extending folded peak edges and folded
valley edges of the material web, as the folding process
progresses. The pattern of the corrugation of the opposite faces
7A' and 8A' is thus selected to correspond to the pattern,
configuration, and dimensions of the partially-formed fold peaks
and fold valleys at the respective selected position along the
transport direction in the folding apparatus, i.e. along the
folding process.
FIG. 9 shows a further possible arrangement for supporting or
carrying out the transverse width-wise contraction and folding of
the material web along longitudinally extending fold lines, for
example a particular embodiment of the expansion/contraction rolls
13, 14 shown in FIGS. 3 and 4. This arrangement essentially
comprises two counter-rotating folding rolls 13 and 14 of which the
circumferential surfaces are suitably corrugated in a pattern
matching the transverse or width-wise folding of the material web.
Thus, as the material web passes between these two intermeshing
rolls 13 and 14, the material web undergoes a contraction in the
transverse or width-wise direction perpendicular to the forward
travel direction, and simultaneously an expansion in the vertical
thickness direction.
The schematic diagram of a general folding pattern shown in FIG. 10
serves as a general reference for the explanation of the
subsequently described specific folding patterns, especially with
respect to various dimensions thereof. These folding patterns are
developed in a continuous folding process according to the
invention as described above. Particularly, these are possible
folding patterns of the folded core structure of the composite
structural panel according to the invention. In these schematic
diagrams of the folding patterns, a dashed line indicates a fold
peak P while a solid line indicates a fold valley V. In this
regard, a fold peak indicates a fold angle of >180.degree. about
the fold line as measured on the upper surface of the folded
material web, while a fold valley indicates a fold angle of
<180.degree. about the fold line as measured on the upper
surface of the folded material web. Furthermore, dotted lines
represent construction auxiliary lines with no fold, i.e. a "fold"
angle=180.degree..
FIG. 10 further illustrates the longitudinal dimension or length
L.sub.1, L.sub.2, L.sub. . . . , L.sub.n measured in the
longitudinal direction of the material web from one transversely
extending fold line to the next, e.g. from a fold peak P to the
next fold valley V in the longitudinal direction. Reference
S.sub.1, S.sub.2, S.sub. . . . , S.sub.n identifies the transverse
spacing in the width direction of the material web, between
respective adjacent longitudinally extending fold lines, e.g.
between a fold peak P and the laterally or transversely adjacent
fold valley V. The vertical height of the folded protrusion from
the lowermost to the uppermost portion of a given fold line, e.g.
along a fold peak P or along a fold valley V is respectively
identified by V.sub.1, V.sub.2, V.sub. . . . , V.sub.n. As will be
discussed next in connection with specific examples as shown in the
following figures, each one of these respective dimensions can be
the same or different in successive segments of the repeating fold
pattern.
FIG. 11 shows a simple zig-zag fold pattern with the characteristic
that V.sub.1 =V.sub.2 =V.sub. . . . =V.sub.n, and S.sub.1 =S.sub.2
=S.sub. . . . =S.sub.n, and L.sub.1 =L.sub.2 =L.sub. . . .
=L.sub.n.
FIG. 12 shows a zig-fold pattern in which the vertical height and
the lateral spacing of each adjacent pattern segment remains the
same, namely V.sub.1 =V.sub.2 =V.sub. . . . =V.sub.n, and S.sub.1
=S.sub.2 =S.sub. . . . =S.sub.n, but the longitudinal length of
successive segments of the patterns varies, namely
L.sub.1.noteq.L.sub.2.noteq.L.sub. . . . .noteq.L.sub.n.
FIG. 13 shows a further more-complex variant of a zig-zag fold
pattern in which only the vertical height remains consistent, while
the lateral spacing and the longitudinal length vary. Namely, in
this fold pattern V.sub.1 =V.sub.2 =V.sub. . . . =V.sub.n, while
S.sub.1.noteq.S.sub.2.noteq.S . . . .noteq.S.sub.n, and
L.sub.1.noteq.L.sub.2.noteq.L.sub. . . . .noteq.L.sub.n.
FIG. 14 illustrates another complex zig-zag fold pattern of which
the transverse width or spacing between the longitudinal fold lines
remains consistent, i.e. S.sub.1 =S.sub.2 =S.sub. . . . =S.sub.n,
but the vertical height of the folds varies and the longitudinal
length or spacing between successive transverse fold lines varies,
i.e. V.sub.1.noteq.V.sub.2.noteq.V.sub. . . . .noteq.V.sub.n, and
L.sub.1.noteq.L.sub.2.noteq.L.sub. . . . .noteq.L.sub.n.
FIG. 15 shows a fold pattern that is based on a simple zig-zag fold
pattern with consistent dimensions, i.e. V.sub.1 =V.sub.2 =V.sub. .
. . =V.sub.n, and S.sub.1 =S.sub.2 =S.sub. . . . =S.sub.n, and
L.sub.1 =L.sub.2 =L.sub. . . . =L.sub.n, but an additional
intermediate web 22 is interposed at each longitudinally extending
fold peak and each longitudinally extending fold valley.
FIG. 16 illustrates a simple counter-directed fold along successive
alternating round contours with uniform or consistent dimensions or
spacings in the vertical, transverse, and longitudinal directions,
namely V.sub.1 =V.sub.2 =V.sub. . . . =V.sub.n, and S.sub.1
=S.sub.2 =S.sub. . . . =S.sub.n, and L.sub.1 =L.sub.2 =L.sub. . . .
=L.sub.n. In this context, rather than round curved contours, the
curves could follow elliptical, hyperbolic, or essentially any
other desired curvature.
FIG. 17 shows a fold pattern generally similar to that of FIG. 16
with round or curved contours, but in this case having a varying
vertical height. Namely, V.sub.1.noteq.V.sub.2.noteq.V.sub. . . .
.noteq.V.sub.n, while S.sub.1 32 S.sub.2 =S.sub. . . . =S.sub.n,
and L.sub.1 =L.sub.2 =L.sub. . . . =L.sub.n. Once again, the curves
may have a circular, elliptical, hyperbolic, or essentially any
other desired curved contour.
FIG. 18 shows a simple uniformly or consistently directed fold
along curved contours, with all of the pertinent dimensions being
uniform or consistent, i.e. V.sub.1 =V.sub.2 =V.sub. . . .
=V.sub.n, and S.sub.1 =S.sub.2 =S.sub. . . . =S.sub.n, and L.sub.1
=L.sub.2 =L.sub. . . . = L.sub.n. Once again in this case, the
curved fold lines can have a circular, elliptical, hyperbolic, or
essentially any other desired curved contour.
FIG. 19 shows a fold pattern with uniformly or consistently
directed curved fold lines, but with variations in the vertical
height and in the longitudinal length of successive segments.
Namely, V.sub.1.noteq.V.sub.2.noteq.V.sub. . . . .noteq.V.sub.n,
and S.sub.1 =S.sub.2 =S.sub. . . . =S.sub.n, and
L.sub.1.noteq.L.sub.2.noteq.V.sub. . . . .noteq.L.sub.n. Once again
in this example, the curved fold lines can have a circular,
elliptical, hyperbolic, or essentially any other desired curved
contour.
FIGS. 20 and 21 schematically represent examples of folding
patterns in which the folds in one direction may be curved or bent
in such a manner so that channels are formed in the material web by
the folding process, such that these channels remain open in the
circumferential direction.
Although the invention has been described with reference to
specific example embodiments, it will be appreciated that it is
intended to cover all modifications and equivalents within the
scope of the appended claims. It should also be understood that the
present disclosure includes all possible combinations of any
individual features recited in any of the appended claims.
* * * * *